The present invention involves the ejection of ink drops by way of forming gas or vapor bubbles in a bubble forming liquid. This principle is generally described in U.S. Pat. No. 3,747,120 (Stemme). Each pixel in the printed image is derived ink drops ejected from one or more ink nozzles. In recent years, inkjet printing has become increasing popular primarily due to its inexpensive and versatile nature. Many different aspects and techniques for inkjet printing are described in detail in the above cross referenced documents.
Completely immersing the heater element in ink dramatically improves the printhead efficiency. Much less heat dissipates into the underlying wafer substrate so more of the input energy is used to generate the bubble that ejects the ink. This has allowed the Applicant to develop ‘self cooling’ printheads that do not require any active cooling systems. In self cooling printheads, the print speeds are restricted by paper feed systems and ink chamber refill times rather than heat sinking considerations.